GB2084691A

GB2084691A - Energy absorber

Info

Publication number: GB2084691A
Application number: GB8031226A
Authority: GB
Original assignee: Britax Excelsior Ltd
Current assignee: Britax Excelsior Ltd
Priority date: 1980-09-26
Filing date: 1980-09-26
Publication date: 1982-04-15
Also published as: JPS5761836A

Abstract

An energy absorber consists of a flat metal strip 10 configured into a corrugated or serpentine shape with a slot 16 provided in each limb of each loop. A strap 18 for attachment to a safety harness is threaded in and out of consecutive slots so that it passes round the crest of each loop so that, when a pre-determined strap tension is exceeded, the loops of the strip 10 are straightened. The end portions 12 and 14 of the strip have various kinds of protection means to inhibit chafing of the strap. The end portion 12 may be bent to present a rounded surface, or covered by a longitudinally split sleeve. The end portion 14 may be provided with a guide to keep strap & strip aligned. <IMAGE>

Description

SPECIFICATION Energy absorber This invention relates to an energy absorber which may be used, for example, with a safety harness as worn by telephone linesmen or window cleaners.

A conventional safety harness for a telephone linesman or window cleaner comprises a belt which is fitted around the user's abdomen and a strap or straps which are each fixed at one end to a snap connector. The snap connector is coupled to a fixed eye which is fitted, for example, adjacent a window frame. If the user slips on the window ledge, the straps check his fall. Whilst such harnesses prevent serious accidents, some injury can be caused by abruptly checking the users fall as the strap or straps are relatively inextensible.

British Patent Specification No. 1,536,354 discloses an energy absorber for use with a harness of the foregoing type, consisting of a deformable member of serpentine or corrugated shape with apertures in the loops thereof. The strap connecting the safety harness to the fixed eye is threaded in and out of adjacent apertures so that it takes up the shape of the loops. The material of the member is such that the corrugations are deformed when a pre-determined strap tension is exceeded and do not recoil to their previous spatial relationship when the tension is removed. Thus the length of the member is effectively increased in the direction in which the strap tension acts and energy is absorbed by the recoiless deformation of the corrugations of the member.

The deformable member conveniently takes the form of a metal strip. It is possible that, in some circumstances, the ends of the metal strip may chafe or even cut through the strap. In addition, if the corner of the strip should become embedded in the strap, it could pierce the latter thereby providing a point of weakness. The present invention is concerned with the provision of an improved energy absorber not subject to these disadvantages.

According to the invention, an energy absorber comprises a deformable configured member, said member having apertures therein through which are threaded a strap having free ends adapted for respective connection to a fixed point and a belt or harness, the material and configurations of said member being such that the configurations can be deformed without recoil to their previous spatial relationship when a pre-determined strap tension is exceeded, whereby the length of said member is effectively increased in the direction in which said strap tension acts and energy is absorbed by the recoiless deformation of the configurations of said member, at least one end of said member having protection means adapted to inhibit chafing or cutting of the strap thereby.

In one form of the invention, said one end of said member is bent out of the path of said strap, the rounded surface formed thereby comprising said protection means.

In another form of the invention, wherein the protection means comprises a longitudinally split tube embracing an end edge of the deformable member.

Alternatively or additionally, guide means may be provided for maintaining the strap in alignment with said one end of the deformable member.

Two embodiments of the invention will now be described by way of example, with reference to the accompanying drawings, in which, Figure 1 is a perspective view of one form of an energy absorber in accordance with the invention, and Figure 2 is a perspective view of an energy absorber in accordance with another form of the invention.

Referring to Figure la a flat metal strip 10 is configured into a corrugated or serpentine shape along its length between its end portions 12 and 14.

A respective slot 16 is provided in each limb of each loop. A strap 18 is threaded in and out of consecutive slots 4 so that it passes round the crest of each loop and takes up the corrugated or serpentine shape of the metal strip 10. In use, one end of the strap 18 is attached to a fixed point and the other to a safety harness for a workman, the length of the strap- 18 being such as to give the workman reasonable freedom of movement. The strip 16 is preferably made from a metal such as steel an is of a thickness such as to resist straightening of the loops when the strap 18 is tensioned under normal use. For example, the user may lean back without straightening the loops.However, when a pre-determined strap tension is exceeded such as that encountered if the user falls from a height, the loops of the strip 10 are straightened, without recoil to their previous spatial relationship thereby absorbing the shock of the fall.

In accordance with the invention, the end portions 12 and 14 of the strip 10 are formed with a curved configuration similar to a continuation of the corrugated shape of the strip. Consequently, the ends of the strap 18 are led over the outer curved surfaces of these end portions rather than over relatively sharp end edges.

In order to keep the strap 18 aligned over the curved end portion 14, a sleeve 20 is fitted over the latter. The sleeve 20 has edge portions 22 which are an interference fit on the edges of the strip 10, and a central portion 24 which defines a channel through which the strap 18 is led. There is thus no possibility of the strap 18 being displaced from the outer curved surface of the end portion 14. Another sleeve similar to the sleeve 20 is preferably fitted to the end portion 12 but this has been omitted from the drawing for the sake of clarity.

Figure 2 illustrates another form of energy absorber comprising a metal strip 30, the central part of which is similar in shape to the strip 10 of Figure 1, having corresponding slots 32 in each limb of each loop through which a strap 34 can be threaded.

However, the end portions 36 and 38 comprise edges which are covered by split tubes such as the tube 40 on the end portion 36 so as to provide a relatively large radius curve. A similar split tube is provided on the end portion 38 but this is not visible because it is enclosed within a sleeve 42, generally similar to the sleeve 20 of Figure 1 apart from protuberances 44 and 46 to accommodate the ends of the split tube and other differences due to the differently shaped end portion. As with the embodiment illustrated in Figure 1, a sleeve similar to the sleeve 42 is fitted to the end portion 36 but, once again, this has been omitted for the sake of clarity.

Guide means such as the sleeve 42 may be used with an energy absorber as described in the above mentioned Patent Specification, i.e. as illustrated in Figure 2, but without the split tube 40.

Claims

1. An energy absorber comprising a deformable configured member, said member having apertures therein through which are threaded a strap having free ends adapted for respective connection to a fixed point and a belt or harness, the material and configurations of said member being such that the configurations can be deformed without recoil to their previous spatial relationship when a predetermined strap tension is exceeded, whereby the length of said member is effectively increased in the direction in which said strap tension acts and energy is absorbed by the recoiless deformation of the configurations of said member, at least one end of said member having protection means adapted to inhibit chafing or cutting of the strap thereby.

2. An energy absorber according to claim 1, wherein said one end of said member is bent out of the path of said strap, the rounded surface formed thereby comprising said protection means.

3. An energy absorber according to claim 1, wherein the protection means comprises a longitudinally split tube embracing the edge of said one end of the deformable member.

4. An energy absorber according to claim 1, 2 or 3, wherein the protection means comprises guide means for maintaining the strap in alignment with said one end of the deformable member.

5. An energy absorber according to claim 4, wherein the guide means comprises a sleeve having outer portions dimensioned to be an interference fit on the end of the deformable member and a central portion forming a channel through which the strap can be threaded.

6. An energy absorber according to any preceding claim, wherein the deformable member is configured in a serpentine or corrugated shape defining a series of loops and the apertures are present in each of the loops and the strap is threaded in and out of adjacent apertures so as to take the shape of the loops.

7. An energy absorber for a safety harness substantially as hereinbefore described, with reference to the accompanying drawings.